The contractor will test the efficacy of the standard off-label acute radiation syndrome (ARS) countermeasure, rhG-CSF (Neupogen[unreadable]), and one other countermeasure, at the LD70 radiation dose for the hematopoietic syndrome. In addition, we will use a sublethal radiation dose for complete hematological time courses without censorship of data due to mortality. We will assess the effects of radiation injury and rhG-CSF using the following endpoints: circulating neutrophils, monocytes, platelets, red blood cells, lymphocytes, and hematopoietic progenitor cells;blood chemistry, platelet function, coagulopathy, and histopathology of multiple organ systems.